Summary of findings for the main comparison. Summary of findings: omega‐3 fatty acid supplementation compared with placebo for cystic fibrosis.
| Omega‐3 fatty acid supplementation compared with placebo for cystic fibrosis | ||||||
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Patient or population: children and adults with cystic fibrosis Settings: outpatients Intervention: oral omega‐3 supplementation (EPA or DHA, or both) Comparison: placebo | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect (95% CI) | No of Participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Assumed risk | Corresponding risk | |||||
| Placebo | Omega‐3 supplementation | |||||
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Number of pulmonary exacerbations (median number of exacerbations during the study) Follow‐up: 12 months |
The number of exacerbations in the placebo group was greater than in the omega‐3 group (3.5 versus 1.7 (range 1 ‐ 3)). | N/A | 13 (1) | ⊕⊝⊝⊝ very lowa,b | The authors only report the number of exacerbations in the supplemented group compared to the 12 months prior to the trial. Extra data was provided by the study authors to allow a between group comparison. This outcome was not included in the study protocol. |
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Adverse events: diarrhoea Follow‐up: 6 weeks |
1 study reported drop out due to diarrhoea. 2 out of 7 participants in the fish oil group dropped out and 2 out of 5 participants in the placebo group, OR 0.6 (0.05 to 6.79). | OR 0.6 (0.05 to 6.79) | 12 (1) | ⊕⊝⊝⊝ very lowc,d | Other adverse events included stomach pains (5/35 participants) but the intervention arm wasn't specified (Keen 2010). | |
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FEV1 % predicted Follow‐up: 6 months |
The mean FEV1 % predicted was 64% in the control group. | The mean FEV1 % predicted in the intervention group was 2% higher (19.1% lower to 23.11% higher) | MD 2.00 (19.11 to 23.11) | 17 (1) | ⊕⊝⊝⊝ very lowb,e | A further study (n = 16) reported a significant increase from baseline in the EPA group compared to the control group measured in L compared to the placebo group (P = 0.06) (Lawrence 1993). Two studies reported no difference in FEV1 % predicted or lung function (measurement not stated) between groups (Hanssens 2016; Keen 2010) |
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FVC % predicted Follow‐up: 6 months |
The mean FVC % predicted in the control group was 81%. | The mean FVC % predicted in the intervention group was 1% lower (16.65 % lower to 14.65 % higher). | MD ‐1.00 (‐16.65 to 14.65) | 17 (1) | ⊕⊝⊝⊝ very lowb,e | 1 study reported a significant rise in FVC (L) in the EPA group (P = 0.01) (Lawrence 1993). 2 studies reported no difference in FVC between groups, but no data were available for analysis (Hanssens 2016; Keen 2010). |
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Growth and nutrition: BMI SD score Follow‐up: 6 months |
No significant difference was seen between the PUFA group and the placebo group after 6 months. | MD 0.00 (95 % CI ‐0.64 to 0.64) | 29 (1) | ⊕⊝⊝⊝ very lowb,e | A further study reported on BMI but reported only that BMI z scores remained stable throughout the study (Hanssens 2016). | |
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Biochemical markers of essential fatty acid status: EPA and DHA % content of neutrophil membrane Follow‐up: 6 months |
1 study reported a higher EPA content of the neutrophil membrane in the omega‐3 PUFA‐supplemented group compared to the placebo group, MD 0.90 (95% CI 0.46 to 1.34). In the same study, no difference was observed in DHA membrane concentration between groups, MD 0.10 (95% CI ‐0.45 to 0.65) |
29 (1) | ⊕⊝⊝⊝ very lowb,e | At 6 months, Keen reported a significant increase from baseline in both EPA and DHA content of serum phospholipids in the omega‐3 supplemented group compared to placebo, MD 0.70 (95% CI 0.42 to 0.98) and MD 1.10 (95% CI 0.39 to 1.81), respectively (Keen 2010). | ||
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). BMI: body mass index; CI: confidence interval; DHA: docosahexaenoic acid; EPA: eicosapentaenoic acid; FEV1: forced expiratory volume in 1 second; FVC: forced vital capacity; MD: mean difference; OR: odds ratio; PUFA: polyunsaturated fatty acid; SD: standard deviation. | ||||||
| GRADE Working Group grades of evidence High quality: further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: we are very uncertain about the estimate. | ||||||
aDowngraded twice due to risk of bias within the included study for this outcome. There was uncertainty around allocation concealment and blinding and a high risk of bias due to selective reporting.
bDowngraded once due to imprecision from very low participant numbers and low event rates.
cDowngraded once due to risk of bias within the included study. It was unclear whether allocation was concealed and whether the outcomes were predefined as there was no protocol available.
dDowngraded twice due to very low participant numbers (n = 12) and low event rates.
eDowngraded twice due to risk of bias within the trial. The risk of bias was unclear across several domains including; randomisation, allocation concealment, incomplete outcome assessment and selective reporting.